Telegraph system



June 2, 1931.

H. F. MAY

TELEGRAPH SYSTEM Filed Nov. 9, 1929 VIE/v mf? H /z-MAY Patented June 2, 1931 UNITED STATES .PATENT OFFICE HAROLD F. MAY, OF VALLEY STREAM, NEW YORK, ASSIGNOR` TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION F NEW YORK.

TELEGRAPH SYSTEM Application filed November This invention relates to telegraph systems and particularly to printing telegraph systems in which the local power'supply for driving the equipment is controlled from a distant point.

The objects of the invention are to reduce the current consumption and maintenance eX- penses incurred in the operation of these systems and to render the equipment effective automatically when required and to disable it when its service is no longer needed.

-A feature of the invention is a system comprising a number of stations interconnected by a single metallic signal conductor together with sources of current at the stations normally disconnected from said conductor, so arranged that when potential is applied to the'line at a calling station the printer driving motors at the other stations are set in operation and continue to run during the line openings and closures caused by the telegraph message signals, and also so arranged that, when a long opening of the line occurs or when potential is removed from t-he line, the motors are automaticallyr stopped.

This invention has been illustrated in the accompanying drawing in which three printing telegraph stations A, B and C have been shown connected by a single conductor L. At these stations well known printing apparatus have been shown in diagrammatic form at l, 2 and 3 respectively. The motor and generator mechanism for driving these printers have been shown also in diagrammatic form at 4, 5 and 6 respectively. The line L is normally connected through these printers and their respective printer contacts and break keys; through contacts of transfer relay and slow release line relay 11 to ground at station A, through the contacts of transfer relay 12 and slow release line relay 13 'at station B in series and through contacts of transfer relay 14 and slow release line relay 16 to ground at station C.

Referring now Vto the operation of the system, the motor generators at two of the stations may be started and later stopped by operations performed at the other station. For example, if the operator at A decides to communicate with the other stations B and C,

9, 192e. yserial no. 406,070.

the motor generators at these latter st-ations would be automatically started as follows: The rst operation on the part of the operator at A would be to close-the double pole switch 18 and thus close the connection for his motor generator at 4 and the motor M of the printer 1 through an obvious circuit from the current supply (not shown) but connected to the conductors 17. The motor at 4 being connected with the generator at 4 now causes the generator to build up a voltage.. This voltage causes the operation of the transfer relay 10 over a circuit from ground through the winding of relay 10, the double pole switch 18 through the generator to ground. Relay 10 now remains energized as long as the switch is closed. Relay 10 in operating opens the connection from relay 11 to line L and connects the line Lto the generator 4 and thus causes current to flow out over the line L to the other stations.

This current causes the operation of line relays 13 and 16 at stations B and C respectively. Referring now to the further operations of the circuits at station C only, the operation of relay 16 closes an'obvious circuit for the operation of relay 25. Relay in operating closes a circuit 20 leading to printer 3 for operatingthev usual printer control relay PCR. This relay in turn closes the connection from the current supply at 26 through conductors 21 for the operation of the motor M of the printer 3. As the switch 27 is open, relay 14 will remain deenergized` at this time. Similarly, at station VB the operation of relay 13 causes the operation of relay 28 which in turn operates the printer control relay PCR through conductor 24 to start the motor M` ofthe printer 2 through conductors 23.V

The circuits at the three stations are now in condition for signaling. This is done in the usual way by opening and closing the printer contacts which are shown in station A at 29. These signals interrupt the current in the line L but as the line relays 13 and 16 are slow to release, they will remain operated during these open periods v of the line. Should, however, either of these relays re-0 lease, the relays 28 or 25-Wi11 remain operated *f esl as they are also slow in releasing, and thus prevent the current supplied to the motor of printers 2 and 3 from being discontinued.

Printers 1, 2 and 3 are individually provided with keys 36, 37 and 38 respectively for transmitting a break signal over the line L. If the line L is opened for a long period such as is usual when a break signal is transmitted, the line relays 13 and 16 and later relays 28 and 25 will release and cause the printers 2 and 3 to stop.

In case it is considered undesirable to have the printers stop during long break signals, high resistances such as 30, 31 and 32 may be inserted across the break keys at the respective 'sta-tions and thus cause sutcient current to flow through the line L upon actuation of any one of the keys. This Will maintain the operation of relays 11, 13 and 16 and yet not interfere with the proper reception of the break signal.

It should be noted that the current supply at lthe generator d is poled with the negative side 39 towards the line L and at the generaF tor 6 with the positive pole 40 towards the line L so that the current in the line Will always be in the same direction. This is a usual arrangement for printing apparatus Where polarized relays aie employed.

The circuit arrangements at station B are somewhat dierent from those at the other stations A and C With respect to the operations when this station is calling. It switch 35 is closed to initiate a call from this station, relay 12 is operated over a. circuit through the generator at 5, switch 35, Winding of relay 12, back to the other side of the generator. Relay 12 in operating disconnects relay 13 from the line by opening the connection at its right-hand armature and back contact and closes a connection for the generator to include it in series with the line by the closing of the connection at the right-hand armature and front contact of this relay. Current from the generator at 5 is thereby supplied to the line and the direction of the current in the line will be the same as When one of the other stations is calling. In all other respects the circuits at all three stations are identical.

It should -be understood that While the invention has been illustrated with but three stations on a line, other stations may be added in the same manner as station B is included and that this disclosure should nierely be considered as illustrative of the invention.

Vhat is claimed is:

1. In a telegraph system, a plurality of stations, a metallic conductor interconnect ing said-stations, a signal receiver at each station, means vat each Ystation for sending telegraph signals over said conductor to operate the receivers at the other stations, a source of current at each station normally `discon-' nected from said conductor, means at a calling station tor connecting its source to said conductor, and means at a called station responsive to the iioiv oi current in said conductor for starting and maintaining the receiver in operation during the sending of telegraph signals over the conductor, said last means serving to discontinue the operation of the receiver when current ceases to floiv in said conductor for a prolonged inb ceiving devices at the other stations for transy initting and receiving signals and for maintaining said receiving devices in condition during the transmission of signals comprising impulses oii said current at certain intervals on the conductor, and means responsive to the interruption of current in the conductor ior a longer interval for disabling the receiving devices.

3. In a telegraph system a plurality of sta` tions, a conductor connecting said stations, a signal transmitter at each station, .a signal receiver at each station, a source of current at each station for supplying the transmitter and receiver with actuating power and signal current for said conductor, means for connecting the source at a calling station to the conductor and to the devices thereat, means at the other stations responsive to current signals received at certain intervals over the conductor .for supplying actuating power from vtheir individual sources of current to their respective receiving devices to make them responsive to said signals, said means becoming ineiiective when an interval between signals is of longer duration.

In testimony whereof, I have signed my name to this specification this 7th day of November, 1929.

HAROLD F. MAY. 

